1. Field of the Invention
The present invention relates to a printed circuit board and method for fabricating the same, and in particular, to a blind hole structure of a printed circuit board and method for fabricating the same.
2. Description of the Related Art
FIG. 1 is a cross section view showing a conventional printed circuit board 50. Solder balls 136 of the conventional printed circuit board 50 are formed in openings 128 of a solder mask insulating layer 116 by a conventional solder ball mount process. The conventional solder ball mount process comprises, disposing a printing mold having openings over the solder mask insulating layer. Next, solder paste is scraped or squeezed into the openings of the printing mold, covering surfaces of the solder mask insulating layer 116 and the openings 128. Next, the solder paste on the surfaces of the solder mask insulating layer and in the openings 128 is melted by a reflow process, wherein forming solder balls 136 in the openings 128 of the solder mask insulating layer 116. The conventional solder ball 136, however, only contact the circuit 110 exposed from a bottom side of the opening 128. Thus, if solder paste amount or pressure applied on the printing mold is not enough, some problems of the solder balls, for example, insufficient volume or skip printing, would occur, wherein decreasing reliability of the printed circuit board.
Thus, a novel printed circuit board and method for fabricating the same with improved reliability are desired.